1. Field of the Invention
The present invention relates to a glass fiber product for use in the reinforcement of fluororesin which is improved in adhesiveness to fluoroplastic.
2. Description of the Prior Art
Among the many thermoplastic materials, fluororesin is different from other plastic materials in that it has excellent heat resistance, chemical resistance and dielectric property. For this reason, fluoroplastic has been used in various fields.
Originally, fluororesin is a soft material. In order to compensate this softness, inorganic fillers such as glass fiber, graphite, molybdenum disulfide and the like are used. Among these inorganic fillers, glass fiber is most conventionally used in the field of electrical industry, because of its inexpensiveness and excellent electrical properties. Further, glass fiber greatly improves in the mechanical characteristics such as abrasion resistance, creep resistance, elastic modulus and the like. However, glass fiber is disadvantageous in that the minute gap formed at the interface between glass fiber and fluoroplastic brings about a deterioration in insulation resistance.
The problem of deterioration in insulation resistance makes the greatest trouble in expanding the use of a material in the field of electrical industry.
With the aim of overcoming this disadvantage, various attempts have been made up to today. They are:
(1) An attempt to use a glass fiber in the state of carrying greige goods on its surface, expecting that the interfacial adhesion will be improved owing to the baking effect (the so-called scorching) of the greige goods at the molding temperature of fluoroplastic (350.degree. C. to 400.degree. C.).
(2) An attempt to use greige goods of glass fiber in a state of appropriate scorching without burning them completely, expecting that the adhesion will be improved by the same effect as in (1).
(3) An attempt to apply the hitherto known general silane couplers (for example, a blend of silane couplers, a blend of a silane coupler and a primer such as silicone resin primer, fluororesin primer or the like, etc.).
However, none of these attempts could exhibit any significant effect.
The present inventors conducted many studies on the surface treatment of glass fiber for use in the reinforcement of fluororesin, with the aim of solving the above-mentioned problems.